Lens



Patented Nov.. 16, 1926.

UNITED STATES PATENT'OFFICE.

EDGAR D. TILLYERROF SOUTIIBRIDGE, MASSACHV'USETTS, ASSIGNOR T0 AMERICANOP- TICAL COMPANY, OF SOUTHBRIDGE, MASSACHUSETTS, A VOLUNTARYASSOCIATION or MASSACHUSETTS.

LENS.

Application inea August 7, 1924. seriai No. 730,565.

i The present invention relates toa 'new and useful multifocal lens andto a process for forming two part lenses which are Well known in the artas fused or Kryptok lenses. 1t is a well known fact that in a finishedlens o'f this type the oblique vision through the reading portion isvariable, increasing in power from the center towards the margin, whichis quite a pronounced and objectionable aberration.

An important object of the invention is to provide an improvedmultifocal lens formed of two pieces of glass of different indices ofrefraction which will be practically free from the objectionablevariations present in the reading portion of the prior art lenses ofthis type.

Another very important object of the invention is to provide a new andimproved process for forming two part lenses whereby the objectionableoblique errors will be eliminated so as to produce a reasonably correctvision or visions through the reading portion of the lens. n

.Another very important object of the invention' is to provide amultifocal lens and process for forming the same wherein the finishedlens will have a substantially elliptical shaped button and in which thebutton will be composedof two major meridians, the curvatures of whichwill be different to compensate for the oblique errors. Other advantagesand objects of the invention will become apparent during the course ofthe following description.

Inj the drawings, wherein like numerals are employed to designate likeparts throughout the same: v t

Figure 1 isa top plan view of a lens bla similar to the prior artstructures. Figure 2 is asection taken on line 2 2 in Figure 1.

Figure 3 is a 4perspective view showing aA blank as illustrated 'inFigure 1 after the first r step of my improved process.

Figure 4 is a top plan view of a blank after it has been' formed inaccordance with the present invention. v

AFigure 5 isa section taken on lin`e 5-5 of4 Figure 4.

Figure 6 is a section taken on line6-6 in Figure 4.

Figure 7 is a diagrammatic view of a cross section of a .bifocal lensshowing oblique vision through the -reading portion.

It will be noted from the diagrammatic view, Figure 7, that the readingportion or segment of a bifocal lens being placed at the bottom of thelens below the center of the eye and below the .optical axis of thedistance pol-tin, practicallyfall the rays of light from the center ofthe eye will ass obliquely through the reading portion. n other words, abifocal lens located in its position of greatest use before the eye ispractically always looked thru in an oblique direction, and it is Y wellknown that oblique vision is not as clear as vision along the opticalaxis or vision that 'goes normally thru the lens.- For this reason`among others, ithas been found that there is considerable variation inthe power at the center of the segment or reading portion of bevariations in. the horizontal or otherplanes and-it is a part of theconception of this invention that these variations in the horizontal,vertical or any other plane may lie-made by providing the necessarymeans for neutralizing the 'error at any given angle or angles. 4 In thedrawings wherein for the purpose of illustration is shown a preferredembodiment of the invention, the numeral 10 designates a multifocal lensblank which is provided with the insert or button 11. Heretofore, therecesses in' which the buttun 11 is fused have been spherical incurvature. The spherical recesses have been objectionable due to thefact that the vision thru the button increased in power from the centretoward the edge thereof so that the true vision has not been-obtainedwhen lookirg through thebutton near the marginal e ge. n In accordancewith thepresent invention, the recess having a spherical .curve isformed in the blank and the button 11 is fused therein. After thisoperation, the blank as illustrated in Figures 1 and 2, is placed uponthe block 12 which has a toric surface formed thereon, i. e., a surfacehaving dierent curvatures in the two major meridiana. In other words,the major meridans of the block 12 which are at right angles to eachother have di'erent curvatures. The blank is then placed on the block l2and sufficient heat is applied to the parts to permit the lens blank tosettle down so as to assume the surface shape 13 of the block l2. As isshown in Figure 3, the button 11 will assume an elptical shape as isshown in Fig. 4.

The action of the lens blank upon the block is clearly shown in Figures5 and 6, in that it is shown with a torio button which is really formedbecause of the fact that the glass is so bent over the block under theaction of heat that the button is bent or distorted into an ellipticalshape having a minor and a major meridian of different curvatures. 'Itwill be seen from the foregoing that the spherical countersink has beenbent to a toric surface shape. l

A slight modification includes heating the button and blank together tofuse the button into the recess, after which the heatv is increased soas to let the blank drop to a torio shape, thus bendingthe button as inthe first instance, britain one continuous operation.

lt is to be understood that the button will not necessarily7 have toassume the elliptical shape positioned as shown in Figure 4 'because themeridians can be shifted to any required angular position to neutralizethe oblique errors to desired requirements.

It will, therefore, be seen from the foregoing that I have provided alens and process for forming the. same whereby the amount of obliqueerrors present in the but ton or reading portion has been reduced to aminimum, and neutralized as desired.

llt is to be understood that the form of the invention herewith shownand described is to be taken as the preferredembodiment of the same andthat various changes in the size, shape and arrangement of'parts may beresorted to without departing from the spirit of the invention or thescope of the subjoined claims.

Having thus described my invention, claim:

1. A blank for making a multifocal lens comprising a major blank of oneindex of refraction having a finished lens seat on one side thereof, aminor blank of a different l index of refraction having a finishedsurface secured to the lens seat of the frstblank and a bend throughoutthe body of the major blank f a curvature in one meridian of a magnitudeto neutralize the inherent astigmatism of the minor portion of thefinished lens.

2. A blank for making a multifocal lens 'comprising a. ma'or blank ofone index of refraction having a finished spherical lens seat on oneside thereof, a minor blank of a different index of refraction havin afinished surface secured to the curved lens seat of the first blank anda bend throughoutrthe maor blank of a curvature in one meridian o amagnitude to neutralize the inherent astigmatismof the minor portion ofthe finished lens. f

EDGAnD. TILLYER.

